A challenge in modern product packaging has been to provide container caps or closures that are aesthetically interesting to the consumer, provide brand differentiation, are light-weight in construction, economical to produce, and effectively seal the liquid contents of the container. In order to prevent leakage, conventional closures have been generally designed with flat, uniform top surface configurations so that the underside of the closure has a correspondingly flat annular surface for mating with the flat annular neck rim at the mouth of the container. This situation has heretofore limited the freedom of packaging designers in developing interesting cap configurations while still providing a satisfactory liquid seal.
An improved closure is desired that allows different and irregular configurations to be utilized without sacrificing the integrity of the liquid seal.